Method of and device for cooling dental tools, such as drills or the like



.July 26, 1938.

l w. 4Roos METHOD 0F AND DEVICE FOR COOLING DENTAL TOOLS, SUCH AS DRILLS OR TITIE LKE Filed Dec. 23, 1935 3 Sheets-Sheet 1 u vr vll'Il,"11111111111151111111n filippini,

July 26, 1938. w. Roos 2,124,831

METHOD 0F AND DEVICE FOR COOLING DENTAL TOOLS, SUCH AS DRILLS OR THE LIKE Filed Dec. 2'5, 1935 s sheets-sheet 2 1wIIIIIIInIIIIIIIIlI/l/wlln fraz zQ/x/ w. Roos 2,124,831

SUCH AS DRILLS OR THE LIKE Filed Deo. 2s, 1955 July 26, 1938.

METHOD OF AND DEVICE FOR COOLING DENTAL TOOLS,

5 Sheets-Sheet 3 liee/H02? Patented July 26, 1938 UNITED vSTATES PATENT OFFICE Walther Roos, Basel, Switzerland, assigner to Waropa A. G.,V Basel, Switzerland Application December 23, 1935, Serial No. 55,905 In Germany December 31, 1934 f 6 Claims.

'Ihis invention relates to methods of and devices for drilling teeth with lowltemperature at the point of drilling.

Various contentions have hitherto been made concerning the conditions arising within the teeth during drilling of the same as well as the cause of pain that may set in and the measures to be taken for effecting the drilling without or with less pain.

all sensitivity to pain of the entire tooth in order to ensure painless drilling. Based on this contention, it has been proposed to conduct a gaseous mixture of air and a refrigerating medium, such as for example carbon dioxide and ethyl chloride against the tooth for thus incrusting the same with ice. Such a treatment is, however, not only painful, but may destroy the lifev of the pulp and thus damage the tooth lastingly, Another prior proposal is based on the belief that the drill becoming hot together with the mechanical action of the drilling chips accumulating at the place of drilling, by eiect of which the heating is increased, is the primary cause of the pain. It was proposed to avoid the drill becoming hot by supplying a stream of an adequately cooled medium to the drill head and the place of drilling and to obtain cooling of the entire tooth as well as keeping the drilling chips away from the place of drilling. But, also a procedure of this kind does not give the desired result of painless drilling, since neither the removal of the heat generated by the drilling nor keeping the drilling chips away nor slightly cooling the entire tooth can obviate the condition which now appears as the real cause of pain which consists in vibration of the albuminous substance contained in the odontoblasts.

The present invention is based on the belief and theory that the circumstance mentioned immediately above is actually the real causeof the pain suffered during the drilling of a tooth.

Starting from this realization, the present invention, in departing from prior proposals, is based on an entirely novel principle, namely, of avoiding vibration of the albuminous substance during the drilling operation by reducing the temperature of the albuminous substance in close proximity to thel point of the drilling to below its coagulation temperature without reducing the temperature of the rest of the tooth to below a harmful point.

According to the present invention, this result is accomplished, while purposely preventing the cooling medium from contacting directly with One contention was to temporarily eliminatethe tooth or the place of drilling, by indirectly excessively cooling the drill head by cooling the shank of the drill by means of a cooling medium, such as for example, liquid or highly compressed gaseous carbon dioxide and thereby producing, by the 'excessive reduction of .heat by the drill head, the formation on the outer ends of the individual odontoblasts, that is, the ends adjacenty to the drill head, a plg of coagulated albuminous substance and which serves as a vibration insulation and prevents the transmission of the vibrations to the albuminous substance contained in the odontoblasts or prevents the generation of vibrations therein and thus normally prevents or reduces the feeling of pain. On the continuance of the drilling, this initially formed insulating layer is, however, ground or cut away with the progressive removal of tooth substance by the drilling, but simultaneously therewith a further parallel insulating layer of coagulated material is formed behind the initial layer. In this way it is ensured that an insulating layer is present at all times since the drill being cooled down to an excessively low temperature extractsheat continuously from the adjacent portions of the albuminous substance with the effect of coagulating the same and thus replenishing the insulating layer against transmission'of vibrations to the albuminous substance beneath.

Accordingly, the method according to the present invention consists in cooling a dental drill by means of a compressed cooling medium, as for example, liquid or highly compressed gaseous carbon dioxide, in such manner, that the cooling medium, for instance the said carbon dioxide, is supplied to a hollow space provided on the shank of the drill in liquid or highly compressed gaseous state at a pressure corresponding to its pressure of evaporation at the temperature of the surrounding air, that is, at about to 60 atmospheres. In this space the pressure of the cooling medium is released at least partly, whereupon the cooling medium, for example, the carbon dioxide gas, which may be still under pressure, is removed through a discharge conduit. In order to carry out the method according to the invention properly, a drilling handpiece or angle hand piece can be used in the interior of which a supply conduit for admitting the cooling medium to the drill, a hollow space surrounding a portion of the shank of the drill, and a discharge conduit for the cooling medium, for example the pressure released or gaseous carbon dioxide, are provided. In the hollow space or on the shank of the drill, means, such as for example, ribs,

grooves, spherical polished masses of material or the like, may be provided for the purpose of fs` cilitating the transmission of cold and increasing the cooling capacity. The portion of the drill inside the handpiece and not exposed to the cold is, advantageously, insulated against transmis- `sion of cold as well as the discharge conduit for according to the invention are illustrated by way' of example only:

Fig. 1 shows a longitudinal section through the front half of a first embodiment of the drilling handpiece; I

Fig. 1a shows a longitudinal section through the rear half thereof;

Fig. 2 shows a front elevation of Fig. 1,;

Fig. 3 shows a section on the line III-11'! in Fig. 1;

Fig. 4 is a sectional view taken on the line IV-IV in Fig. 1;

Fig. 5 shows a side `elevation of this drilling hand-piece on a smaller scale:

Fig. 6 illstrates the manner of connecting the drilling handpiece to a carbonic acid steel cylinder;

Fig. 'I shows a longitudinal section through the front part of a second embodiment ofthe drilling handpiece;

Fig. 8 shows a longitudinal section through the rear part thereof;

Fig. 9 shows a section onthe line IX--IX of Fig. 8, and

Fig. 10 shows a longitudinal elevation of this drilling handpiece on a smaller scale.

Fig. 11 shows a longitudinal section of a variant construction of the ilrst embodiment;

Fig. 12 shows a fragmentary section on the l une :n1- 1min Fig. 11:

Fig. 13 is a section on the line XIII-XIII of Fig. Vl1, and

Fig. 14 is a section on the line XIV-XIV of Fig. 1.

In the first embodiment, a laterally projecting detachable hose union 2 for the cooling medium, for example liquid or highly compressed gaseous carbonic acid, is arranged and a flexible conduit 3 is connected thereto, which withdraws the carbonic acid from a steel cylinder [which to this end is mounted upside down. Following the normal shut-of! valve of the carbonic acid steel cylinder an emergency valve I. for cases of ruptures arising in the flexible conduit, is arranged in advance oi'. this conduit. The carbonic acid is supplied to a rotary piston valve I through a conduit` la on the handpiece so as to pass through a small passage l into a hollow space I which surrounds the drill shank 9 (at least partly) alici in which the carbonic acid is partly released from pressure, thereby cooling down considerably and possibly changing to the gaseous state and finally escaping through a passage of the valve C opposite to the passage 1 and through a conduit lb into the atmosphere. 'Ihe flexible conduit 8 as well as the adjoining conduit la are at a pressure which corresponds to its pressure of evap- Ia stop plug il engages.

eration at room temperature,` that is, from about 50 to 60 atmospheres. The drill head I2 is surrounded by a heat tinsulating sheath Il and the piston vvalve 0 as well as the discharge conduit Ib themselves consist of insulating material, in order to prevent conduction of cold to the handpiece as much as possible.

The piston valve 8 is provided along one quar ter of its periphery with a groove I0 -into which k When the part of the piston projecting out of the handpiece is turned by hand in the direction of rotation of the drill for V4 ofa revolution the supply of carbonic acid is interrupted.` By turning this part in the opposite direction the'cooling medium is supplied to the space l again. For rendering the grasping by hand of the piston valve, which is nevertheless considerably cooled, more convenient, the front part of this valve is provided with ribs.

The explanations givenabove with reference to a straight handpiece hold good also for an angie handpiece which may accommodate the hollow space, in which the cooling medium acts on the drill, in its angular projection. Such an arrangement is illustrated in Figs. 11 to 14 in which like and equivalent parts are designated by like numerals. For the sake of cleamess, the valve I and the discharge conduit `lb are here omitted, sealing means of the cooling space on the drill shank, however, being shown. The drill i head I2' is in the form of a continuous sleeve passing longitudinally all the way through the space l and ending in conical bearing portions engaging into mating bearing portions in the end walls of the space l, thereby providing sealing joints against leakage of the cooling medium at both exits of the space 8 for the drill shank. For sealing the entrance of the driving spindle 22 to this space a stuffing box 2l is provided in the bore of the driving-spindle adjacent to the space l. The other joints on the handpiece requiring sealing are made tight against the pressure of the cooling medium, for example, by hot shrinking the parts concerned on one another or by providing a tight sliding t between these parts and so forth.

By virtue of the intensive cooling of the drill shank by action of the cooling medium, the point of the drill is quickly and continuously cooled down to temperatures below approximately minus 10 to minus 30 degrees C., in such manner, that the portions of the dentine contacted by the drill are etlectively cooled, so that, it appears, the insulating layers of coagulated albuminous substance referred to above are formed and vibrations of the inner portions of the albuminous substance and thus the cause of pain is prevented from arising. With the aid of highly compressed gaseous carbonic acid, temperatures ofminus C. are obtainable by causing the pressure to drop down to atmospheric pressure rapidly.

In the second embodiment of the drilling handpiece, 'a rotatable drill head or driving element is provided which, by means of a conical bore, carries along for common rotation the correspondingly tapering inserting end of the drill the diameter of which is not reduced according to a taper towards the cutting head of the drill.

With this construction the advantage is obtained that, apart from enabling connection of the drill to the driving element in simple manner by means of the mating conical portions, the transmission of heat through the drill decreases in the direction towards the reduced end thereof thus permitting disposal of a larger amount of its free end, a correspondingly increased conduis` tion of heat away from the cutting end of the drill is obtainedas compared to arrangements wherein the drill tapers in conventional manner towards the cutting end. .A

As is evident from Fig. '7, the drill 0 is inserted with its conically tapering end portion 8a into a corresponding conical end portion of the bore I 5a of the driving element I5. The remaining portions of the length of the bore Ila are cylindrical and accommodate a pin I8 which permits of pushing the drill 8 out of the driving element I5 in which it is held merely by clamping effect.

The driving element I5 is secured to a spindle I1 by means of which the drill is driven by an electric motor. The driving spindle I1 is provided with a guide slot Ila for a flat stop member I8 having an offset rear end which interengages with an exterior sleeve I9 which is pushed on the spindle I1. By means of the slidable sleeve I9 the stop member I8 can be shifted in the direction of the arrow shown in Fig. 8. 'Ihe stop member I8, thus moved in unison with the sleeve I9, shifts in turn the ejector pin I6, so that the engagement of the drill with the driving element I5 is loosened and the drill is pushed out of the latter.

In a rear extension 20 of the drilling handpiece I two diametrically opposed longitudinal slots 20a are provided through which the slidable sleeve I9 can be gripped by two fingers of the hand, when it is desired to shift the same. During insertion of a drill in'the driving element I5 the ejector pin I6 is pushed back again, by the pressure thus exerted on the drill, in consequence of which the ejector pin in turn pushes back the stop member which during this return movement takes along the slidable sleeve I9 by aid of its shouldered end.

The drill 9 is cylindrical from its conical rear end portion to its cutting end and is thus not tapered over this length, but rather of uniform diameter from the space 8 to which heat is transmitted from the drill away from the cutting end thereof in which way an eiective cooling of the cutting end of the drill is ensured.

Apart from the piston valve 8, also the driving element I5 for receiving the drill 9 by means of its conical bit engaging end is made of a material having effective heat insulating properties. By virtue of the taper accruing from the conical shape ci the inserting end of the drill the conduction of heat forwardly is checked, whilst at the same time additional circumferential space for the heat insulating driving element I5 is afforded, so that admission of heat and extraction of heat from the handle portion of the handpiece is minimized.

I do not limit myself to the particular size, shape, number or arrangement of parts as shown ancldescribed, all of which may be varied without going beyond the scope of my invenion as shown, described and claimed.

What I claim is:

l. The method of drilling teeth comprising cooling the drill to a temperature of approximately from 10 C. to 30 C., while applying the cold drill to the tooth to be drilled, withdrawing heat from the tooth through the drill, continuously withdrawing' said heat from the drill during the drilling, the portion of the tooth immedlately' adjacent the point of drilling being reduced in temperature below the coagulation temlperature of the albuminous protoplasm of the tooth so that the protoplasm immediately adjacent the point of drilling is coagulated and solidifled and fixed in position relative to the dentine tubes, so as to prevent application of vibrations incident to the\drilling to the uncoagulated protoplasm, ondontoblast and pulpa of the tooth.

2. In a device for cooling dental tools, such as drills or-the like. a drilling handpiece, driving means' for the drill mounted in said handpiece, a controllable supply conduit for a compressed cooling medium for cooling said drill provided on said handpiece, a hollow space communicating with said supply conduit provided in said handpiece to surround the shank of said drill at least partly and sealed at `the exit therefrom of said drill shank, a discharge conduit for the pressure released cooling medium communicating with said hollow space, and heat insulating means protecting the portions of said handpiece not. contacting with said cooling medium.

3. In a device for cooling dental tools, such as drills or the like. a drilling angle handpiece, driv- 'ing means for the drill mounted in said handpiece, a controllable supplyconduit for a compressed cooling medium for cooling said drill provided on said handpiece, a hollow space communlcating with said supply conduit provided in said handpiece to surround the shank of said drill at least partly and sealed at the exit therefrom of said drill shank, a' discharge conduit for the pressure released cooling medium communicating with said hollow space. and heat insulating means protecting the portions of said handpiece not contacting with said cooling medium.

4. In a device for cooling dental tools, such as drills or the like, a drilling handpiece, a drill having a cylindric shank rearwardly of its cutting end, a rotatable driving element for said drill mounted in said handpiece, a conical bit engaging bore in said driving element receiving a mating tapering inserting end of said drill, a controllable supply conduit for a compressed cooling medium for said drill provided on said handpiece, a hollow space communicating with said supply conduit provided in said handpiece to surround said shank of said drill at least partly and sealed at the exit therefrom of said drill shank, a discharge conduit for the pressure released cooling medium communicating with said hollow space, and heat insulating means protecting the portions of said handpiece not contacting with said cooling medium.

5. In a device for cooling dental tools, such as drills or the like, a drilling handpiece, a rotatable driving elementf for said drill mounted .in said handpiece, a driving spindle secured to said driving element rearwardly thereof, a conical bit engaging bore in said driving element receiving a mating tapering inserting end ofsaid drill and merging rearwardly of the bit engaging portions with a cylindric through-bore oi said spindle, an ejector pin slidably arranged in said throughbore, a slidable sleeve operatively connected with said pin mounted in said handpiece to be controllable from outside for ejecting said drill by means of said pin, a controllable supply conduit cating with said hollow space, and heat insulating means protecting the portions of said handpiece not contacting with said cooling medium.

6. In a device for cooling dental tools, such as drills or the like, a drilling hand-piece. a rotatable driving element for said drill mounted in said hand-piece, a slotted driving spindle secured to said driving element rearwardly thereof, a conical bit engaging bore in said driving element receiving a mating tapering inserting end of said drill and merging rearwardly of the bit engaging portions with a cylindric through-bore of said spindle, an ejector pin slidably arranged in said through-bore, a sleeve slidably arranged on said driving spindle to be controllable from outside, a stop member for said pin guided in a slot of said driving spindle and bearing against said slidable sleeve'for ejecting said drill by means oi said pin on corresponding control of said slidable sleeve. a controllable supply conduit for a compressed cooling medium for cooling said drill provided on said hand-piece, a hollow space cornmunicating with said supply conduit provided in said handpieee to surround the shank of said drill at least partly and sealed at the exit therefrom of said drill shank. a discharge conduit for the pressure released cooling medium communicating with said hollow space, and heat insulating means protecting the portions of said handpiece not contacting with said cooling medium.

WALTHER ROOS. 

